5x 400gbit running to a 2U box whoa, the PCI lanes must have heat shielding.

More seriously there is a sensibility limit on extreme density where it's not needed. The idea that you're just going to magically get 2 TBit/s out of those ports seems unlikely even with tweaked software, and you're stuck with a power and comms hotspot that's liable to dictate the remainder of your network design.

At max utilisation that 2U would take 12 hours to drain, and only 12 hours assuming peak and likely unachievable throughput and the box otherwise being completely out of service. Not a great start